You know what I'm wondering is that Yanessa told Wick that the purpose of the Sundered Houses meeting is for Halovar, Einfasen, and Cormoray to ask Primus Tachonis what the fuck he's doing. But also, crucially, we know for certain that House Halovar was in on the assassination attempt on King Gus, and that the assassination attempt is not a focus of Einfasen's case against Tachonis: that portion of Petra and Ryah's letter was given to Gus, and Demodus's testimony deliberately left it out on Azune and Murray's advice in order not to potentially anger Einfasen, because the Argosians were staying at the Stahlkeep. We also know House Einfasen has suspicions against House Halovar, however, because they've asked Azune to maintain the fiction that he is at least friendly to the Candescent Creed while reporting back to them. So: Is Primus Tachonis going to reveal that Halovar is part of this too? What does that mean for Einfasen, because to be honest I think had Gus been killed the move was indeed to implicate Einfasen.
I think Houses Halovar and Tachonis are aligned in terms of their initial political goals but secretly diverge past a point, and neither knows this, but House Halovar does have suspicions that Tachonis is up to more than what they say (hinted at in the Overture). So they agree to eliminate the weakened and too-moderate House Royce while using Einfasen and Cormoray's natural areas of expertise to take over the police force and arcane institutions, and then later move on Einfasen and Cormoray. However, we know that House Tachonis thought they would get the Deva Vindicta and have immense celestial power on their side, and their ultimate goal is to destroy the Old Path, whereas I think House Halovar is exclusively interested at this time in political dominance. So they both agree on the assassination attempt. However, for House Tachonis, this is if not a backup plan, an auxiliary one, as they expect to have an avenging angel wreaking havoc on the world, whereas for House Halovar, this is possibly the main plan to take out both King Gus and the Revolutionary Council. House Halovar possibly does not know that House Tachonis was attempting the Deva Vindicta ritual, but it's not clear; it depends on how House Tachonis learned that a Halovar was not a suitable sacrifice. They may have attempted it at some point in the past 70 years. Either way, given that the obelisk at Tannesar was defaced to make an angel loyal to House Tachonis and not the priestly houses, I suspect House Halovar was not fully in on this aspect of the plan.
So back to the Halovar-Tachonis shared plans: the assassination attempt is a means to gain control of both Timmony and the Revolutionary Council, greatly increase the reach of the Candescent Creed, and to begin to cast doubt on House Einfasen's ability to run the Revolutionary Guard. House Cormoray meanwhile is probably still useful to them in obtaining magical items from the Archanade and turning the Penteveral to their purposes. And by the time that Einfasen is taken out, House Cormoray is outnumbered once the priestly houses decide to take them. The Candescent Creed and Bellows Fever are spreading north; House Tachonis funds The Totality as far away as Hargood. Political dominance is complete. Maybe House Tachonis even says they have a way to get rid of the druids and doesn't clarify that it's the destruction of the Old Path itself.
However, it's started to go bad on both sides. The Deva Vindicta failed utterly which means there are survivors of both Royce and Davinos, and Aranessa and Julien spoke to Otto Einfasen in person, Occtis left a note, and Demodus's testimony proves that House Tachonis betrayed the alliances of the Sundered Houses and slaughtered Royce. Gus survived the assassination attempt. All three tables have begun to move against House Tachonis's longer term plans, and the other three standing Sundered Houses are about to confront House Tachonis.
Meanwhile, the Halovars are under vague but unspecified suspicion by House Einfasen, but more importantly, Wick is now working against his house and again, the assassination attempt failed. House Halovar got some of what they wanted (Candescent Creed expansion and a reason for a vote of no confidence against the Revolutionary Council); but Gus survived and is likely going to act more decisively against them. Additionally, House Einfasen must be treated by Halovar as an ally for now, but Einfasen as stated has suspicions, as does Cormoray at least against Tachonis, which means they may have a split vote when it comes to the no confidence vote against the Revolutionary Council, and technically speaking, Aranessa is still alive and should get a vote still. This also means Halovar (and Tachonis) can't try to take over the police force because they have no way to get Einfasen.
So: Sundered House meeting in the Villa Aurora. Einfasen brings the charges against House Tachonis, which are quite serious. Does Primus sell Halovar out? That's my big question.